- (1337-1370) Son of Alfonso XI of Castile and his mistress Leonor Núñez de Guzmán and, therefore, half-brother of Pedro of Castile.
- Lord of Aguilar de Campo and Lara, and Lord of Vizcaya.
- Killed by Pedro of Castile (1359). [Pedro, ch. 21]
- His wife, Juana de Lara, was also killed by Pedro of Castile (1359). [Pedro, ch. 23: 96-99]
- Pedro IV of Aragon agreed to hand him over to Pedro of Castile in exchange for the Aragonese towns he had taken during his 1361 invasion of Aragon. [Pedro, ch. 32: 58-60]